Summary

After a pull request is merged, deleting its head branch with the "Delete branch" button in GitHub Mobile (iOS) closes every open pull request that uses that branch as its base. The same button on github.com retargets those pull requests to the merged PR's base branch, as the docs describe.

Steps to reproduce

1. In one repository, open PR A (feature-a → main) and PR B (feature-b → feature-a).
2. Merge PR A.
3. In GitHub Mobile on iOS, open PR A and tap "Delete branch".

Expected

PR B's base changes to main. From Managing branches within your repository:

If you delete a head branch after its pull request has been merged, GitHub checks for any open pull requests in the same repository that specify the deleted branch as their base branch. GitHub automatically updates any such pull requests, changing their base branch to the merged pull request's base branch.

Actual

PR B is closed. Its timeline shows base_ref_deleted, then closed in the same second. It can't be reopened until the base branch is restored.

Doing step 3 on github.com instead retargets PR B to main. I tested both in the same private repository: the mobile app on 2026-10-19 and the web on 2026-10-20.

Environment

• GitHub Mobile for iOS, latest version as of 2026-10-20
• Repository: private, personal account, GitHub Free, "Automatically delete head branches" off